Effect of Nanocrystallization on Discharge Behavior and Microstructure of Plasma Electrolytic Oxidation on AZ31B Alloy

In this study AZ31B Magnesium alloy was pre-treated with surface mechanical attrition process (SMAT), for nanocrystallization, and subsequently plasma electrolytic oxidation was applied. Real-time imaging and microscopic investigation were used to study discharge events to reveal the pre-treatment effect on coating growth. SMAT processing developed a 100 nm nano-crystalline layer. Nano-crystallinity was verified by XRD and TEM studies which showed that treated area has crystalline size of about 30 nm. SEM studies revealed that in first minute number of discharges on nano-crystalline surface was 50% higher than microcrystalline surfaces. Number of discharge channels in both samples became nearly identical in longer treatment times. Most of the changes in growth rate are focused in first 2 minutes of coating. Calculations revealed that for pre-treated sample extracted volume of molten oxide through each discharges is significantly higher than non-treated sample while the number of discharges are less. However, number of discharges decline rapidly. While oxide layer grows the surface reactivity decreases.     

Mechanical and geometrical approaches applied to composite fabric forming

In this paper, we are interested in the forming of composite fabric by deep-drawing. Two approaches (geometrical and mechanical) are proposed for the simulation of the composite fabric forming. The geometrical approach is based on a fishnet model. It is well adapted to preliminary design phase and to give a suitable estimate of the resulting flat patterns. The mechanical approach is based on a meso-structural approach. It allows us to take into account the mechanical properties of composite fabric (fibres and resin) and the various dominant modes of deformation of fabrics during the forming process. During simulation of composite fabric forming, where large displacement and relative rotation of fibres are possible, severe mesh distortions occur after a few incremental steps. Hence an automatic mesh generation with remeshing capabilities is essential to carry out the finite element analysis. Some numerical simulations of forming process are proposed and compared with the experimental results in order to demonstrate the efficiency of the proposed approaches.     

The ANFIS-PSO strategy as a novel method to predict interfacial tension of hydrocarbons and brine

The interfacial tension of hydrocarbons and brine is known as one of the important parameters which are measured in petroleum and petrochemical industries for example the interfacial tension has straight effect on trapping of oil in a reservoir. In the present work the Adaptive neuro-fuzzy inference system (ANFIS) algorithm was used as a novel approach for estimation of interfacial tension between hydrocarbons and brine as function of pressure, temperature, carbon number of hydrocarbon and ionic strength of brine then the particle swarm optimization (PSO) was used to optimize the predicting model parameters.in order to better evaluation of performance of predicting algorithm the coefficient of determination (R²), average absolute relative deviation (AARD) and root mean squared error (RMSE) were estimated for different steps. The outcomes of this investigation expressed that proposed model has high potential for prediction of interfacial tension between hydrocarbons and brine.     

Ridge extraction and its application to surface meshing

Geometrical feature lines, such as ${{\mathcal{C}}}^1Geometrical feature lines, such as -discontinuity lines, lines of curvature, ridges, asymptotic lines, etc., provide useful information about the surface geometry. The inclusion of these lines into a surface mesh contributes to improving the quality of the geometrical approximation, independently from the element size. In particular, if the element size is locally large with respect to the minimal radius of curvature, then the geometrical approximation of the surface will generally be poor. In this case, the presence of ridges in the mesh improves the geometrical approximation. This paper proposes a new method to extract the extremal graph whose graph nodes are the umbilics and the extremal points, and edges are extremal lines. A function is also introduced to classify the extremal lines to be able to select the ridges from a parametric surface. The resulting graph of ridges is then simplified and integrated as a constraint in a classical surface mesh generation via an indirect approach. A numerical example will illustrate the pertinence of this method.

Boris Clémen?onEmail:

     

Characterization of New Wire Gauze-Structured Packing: Experimental Study

Structured packings are usually employed for increasing the surface contact between vapor and liquid in the absorber and distillation of columns. Experimental investigations are performed to present a high-capacity new wire gauze-structured packing, namely, PACK-1300XY, which is the combination of PACK-1300X and PACK-1300Y. The new PACK-1300XY shows improved efficiency of separation and pressure drop. Comprehensive parametric investigations are carried out to calculate the efficiency of mass transfer and the wet/dry pressure drops under different operating conditions. The new wire gauze-structured packing reduces wet and dry pressure drops by more than 10 % in comparison to PACK-1300Y. In addition, PACK-1300XY decreases the height equivalent to a theoretical plate by more than 5 % compared to PACK-1300X.     

碳纤维增强环氧树脂复合材料在切向气流和激光作用下的损伤

实验研究了靶板表面有0.4 Mach(1 Mach=340 m/s)切向空气气流、 0.4 Mach切向氮气气流和无气流时, 976 nm连续激光对碳纤维增强E-51环氧树脂复合材料的辐照效应, 得到了该材料在不同功率密度下的烧蚀规律。实验结果表明: 当样品发生剧烈热分解时, 随热分解气体流出边界的固体颗粒对入射激光有屏蔽作用; 切向气流一方面可以减弱这种屏蔽作用, 有利于辐照区的烧蚀, 另一方面对样品有冷却作用, 不利于烧蚀; 相比于氮气流, 空气流有助于产物的燃烧, 对下游附近区域产生明显的加热作用; 切向空气气流的加载会明显提高扩散到样品表面的氧气浓度, 导致碳纤维发生氧化烧蚀; 三种气流状态下, 当入射激光功率密度在100～800 W/cm²范围内, 随着功率密度的增大, 激光能量的利用效率逐渐降低。     

飞秒脉冲激光入射单层光学薄膜的光场特性数值模拟

飞秒脉冲激光入射光学薄膜形成瞬态光场分布是一个非稳态过程,该过程不同于纳秒脉冲或连续波入射的情形,不能直接采用求解薄膜特征矩阵的方法进行处理。采用多光束叠加的方法建立了超短脉冲入射单层膜的反射率和内部光强分布的理论模型,并根据ZnS薄膜材料的参数和单层增反膜的特点进行了数值计算。结果表明,对单层增反膜,薄膜反射率与脉宽成正比,并随脉宽增加逐渐趋近于连续波入射时的情形。在同一脉宽下,膜层厚度增加,反射率下降,且反射脉冲形状也发生改变。膜层中的光强分布计算结果也明显不同于连续波辐照情形,且薄膜厚度越大,差异越显著,表现为连续波入射时,膜层内的光强分布呈等振幅的波动,而超短脉冲入射时,波动的振幅逐渐增大,在膜层和玻璃分界处达到最大值。